The disclosed invention relates to a dispersant composition comprising at least one block derived from (i) a polyester of a hydroxy substituted carboxylic acid and at least one block derived from (ii) a polyalkylene glycol terminated by a amine group or a hydroxyl group. The invention also provides lubricating compositions containing the described dispersant as well as methods of making and using the described dispersant, including method of making the dispersant, methods of lubricating an engine with a lubricant containing the described dispersant, and methods of reducing sludge deposit formation and/or keeping sludge suspended such that sludge deposits will not form in an engine.
The formation of sludge in engines, and particularly the deposition of sludge on internal engine surfaces is an area of ongoing concern in the lubricant industry. Controlling sludge deposits resulting from the thermal stressing of engine oil formulations is an ongoing problem, especially when considering that engines are being designed to be more fuel efficient. Efficiency improving measures are being accomplished, for example, by driving towards smaller sump sizes, turbocharging, and implementing gasoline direct injection (GDI). These efficiency measures impart greater thermal stress to the engine oil formulations used to lubricate the engine. Greater thermal stress can lead to increased propensity to form deposits and sludge which in turn lead to efficiency losses.
Additionally, ever more restrictive emissions regulations that invariably curb the use of ash-bearing deposit controlling components (because some can poison after treatment devices) amplify the formulating challenges to build robust lubricants with low deposit propensity.
A string of publications, including U.S. Pat. No. 7,816,309, issued Oct. 19, 2010, U.S. Pat. No. 7,820,605, issued Oct. 26, 2010, U.S. Pat. No. 7,928,044 issued Apr. 19, 2011 to Stokes et al., and U.S. Pat. No. 7,820,604 issued Oct. 26, 2010, U.S. Pat. No. 7,858,566 issued Dec. 28, 2010, U.S. Pat. No. 8,067,341 issued Nov. 29, 2011 to Ruhe Jr. et al., and U.S. 2009/0270531 published Oct. 29, 2009 to Ruhe, Jr., teach variations of compositions comprised of at least the reaction product of (A) at least one copolymer obtained by free radical copolymerization, and (B) at least one amine terminated ether compound, along with optional further compounds.
There is a need for new dispersant technology that better controls the deposition of sludge on engine surfaces, that is the formation of sludge deposits on engine surfaces, in view of the changing engine designs and operating conditions, as well as ever more restrictive emissions regulations.